It is known that waterproofing of a junction of low-voltage insulated wires is achieved by enfolding the wire junction in a cover containing therein a putty sealant, compressing the putty sealant between the upper and lower halves of the cover to spread the putty sealant within the cover.
However, where branch wires paralleling the main are connected to the main, the paralleling wires are packed tight in the cover and form gorges that the putty sealant cannot easily enter, resulting in a failure of satisfactory waterproofing.
In order to overcome the above disadvantage, it has been proposed to provide projections on the inner surfaces of the upper and lower halves of a cover so that the projections may wedge into the paralleling wires to spread the wires laterally (i.e., in the width direction of the cover) to form enough space for receiving a putty sealant (see Japanese Utility Model Appln. No. 59-109075). According to this method, however, since the wires are laterally spread, the cover and, attendantly, the wire junction must be larger in dimension.